I know that one of those places being mentioned above might be Shadow Shopper. But, I can say signed up for a highly discounted 30 day Gold trial with them last December, and cannot say I got any spam at all from it; I did get quite a number of legitimate jobs, though. If they had been guilty of these associations in the past, they were not last December. I found it very useful in finding some new contacts of where shops were moving for the new year. I am planning to do another 30 day trial this month.
However, to go back to the topic at hand...I doubt, personally, that any experienced shopper has fallen prey to these schemes, but it is always possible. I did read an article a while back about a judge who fell prey to a Nigerian scam.
But there are probably a lot of newbie shoppers who fall prey...and the changing of the scam to pay for small jobs before hitting hard makes the likelihood worse, IMHO. That is because many newbs seem to not understand "shopping" that well, and without doing enough research, consider it "free money."
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“Lying in bed would be an altogether perfect and supreme experience if only one had a colored pencil long enough to draw on the ceiling."
~Gilbert K. Chesterton